The terms asphalt and bitumen are often used synonymously in the U.S. to refer to a generic class of amorphous, dark-colored thermoplastic materials composed principally of high molecular weight hydrocarbons. The primary source of asphalt is petroleum oil, where it is obtained as the heavy residue which remains after the volatile gasoline and oil components have been removed by distillation.
Asphalt serves primarily as a binder in mixtures of asphalt and mineral aggregates which are employed in the construction of roads and similar traffic-bearing surfaces such as driveways, parking areas and airport runways. As such it generally comprises 4 to 10 weight percent of the mixture, which is sufficient to coat the mineral aggregate. Asphaltic road paving material is sometimes also referred to as asphalt or "blacktop". According to the review article "Asphalt and Bitumin" by Corbett and Urban in Ullmann's Encyclopedia of Industrial Chemistry, Fifth Ed. (1985), Vol. A3, pages 169-188, over 90% of all traffic-bearing areas are constructed with asphalt mixes.
Although asphaltic traffic-bearing areas are compacted by hot rolling, they are still more porous than surfaces of concrete. There is also an upper layer of asphalt-coated aggregate which is directly exposed to sunlight, air, temperature extremes, rain, snow, ice, vehicle exhaust emissions and fluid leaks (primarily engine oil but also gasoline, diesel fuel and antifreeze solutions), and salts used to dissolve snow and/or ice. Additionally, airport traffic-bearing surfaces are exposed to aviation fuel spills, hot jet engine exhaust and, in cold weather, to aircraft deicing fluids. A major problem in cold climates is freeze-thaw damage from ice, but all of the above exposures lead to degradation of asphaltic traffic-bearing materials. As a result a huge amount of money is expended each year to repair or resurface such materials. Thus there is a clear need for a cost-effective way of extending the useful lifetime of asphaltic traffic-bearing areas.
Asphalt is also used in roofing materials. Asphalt composition shingles, which are used as roofing materials on more than 95% of private dwellings in North America according to the above-mentioned Ullmann's article, consist of a glass fiber or cellulosic backing coated on both sides with a filled asphalt and surfaced on the weather surface with mineral granules. The filed asphalt serves as a binder for both the backing material and the mineral granules. Asphalt is also used as both the binder and upper surface of single and multilayer roofing systems. These asphaltic weather surfaces are subjected to many of the same exposures as a roadway, that is, sunlight, air, temperature extremes, rain, snow and freeze-thaw damage from ice, and eventually replacement is required. A cost-effective way of extending the useful lifetime of asphalt composition shingles and other asphaltic roofing surfaces would therefore also be highly desirable.
It is known that fluorochemicals, particularly certain fluorochemical copolymers, can be used to impart water, oil or grease repellency to paper and paper products, and to textile fibers such as nylon used in carpets and upholstered furniture. It is also known that certain fluorochemical copolymers can be used in combination with other substances to improve the resistance of certain construction materials to water and oil damage. For example JP 9286676 A teaches to employ an aqueous emulsion of a fluororesin which is a copolymer of a fluoro-olefin, a carboxylic acid vinyl ester and unsaturated monomers having hydrophilic functional groups with a water emulsion of a silane compound which has hydrolyzable functional groups to form a water-repellent, weather-resistant coating on the surface of cured concrete.
EP-A 0 714 921 teaches two component resin compositions for water-repellent coatings for textiles and building materials which comprise a fluorinated acrylic copolymer component which also contains cationic amino groups, either in salt or quaternized form, and other functional groups, and a polyisocyanate component. On mixing the two water-based components and applying the mixture to building materials, they harden rapidly to a coating which imparts stable water- and oil-repellent, anti-graffiti properties to the treated substrates.
U.S. Pat. No. 5,753,569 teaches a two component coating treatment to render substrates selected from the group consisting of naturally occurring and synthetic textiles and their mixtures, leather, mineral substances, thermoplastic and thermosetting polymers and paper, oil-, water- and soil-repellent by applying thereto compositions containing components A and B, wherein component B is a fluorine-free poly(meth)acrylate ester and component A is fluorine-containing and comprises repeating units from a) 40 to 85% by weight of (meth)acrylates containing perfluoroalkyl groups, b) 1 to 45% by weight of one or more monomers from the group consisting of styrene, acrylonitrile, vinyl acetate, vinyl propionate and (meth)acrylate esters, c) 4 to 30% by weight of (meth)acrylate esters of polyether polyols and d) 1 to 15% by weight of ionic or ionizable monomers which contain either an amino or a carboxyl function.
EP-A 0 714 870 teaches an oleophobic and hydrophobic treatment for certain construction materials which comprises applying to the surface of the materials to be treated a mixture of a water soluble cationic fluorinated acrylic copolymer of the type disclosed in U.S. Pat. No. 5,493,998 and a polymeric film former, polyvinyl alcohol. The copolymers are reaction products of a perfluoroalkylethyl acrylate, a dialkylalkylaminoethyl methacrylate, vinyl acetate and optionally a fourth monomer such as butyl methacrylate. While some protection can be provided by saturating a surface with an aqueous solution of the copolymer alone, the high concentration of the water-soluble cationic fluorinated acrylic copolymer required, 20-25%, makes this approach unattractive and impractical.
None of the above-mentioned references teach how to protect an asphaltic surface. Additionally, all of the above surface treatments, whether they employ cross-linked resins or physical mixtures with a polymeric film former, form coatings which seal the surface of the substrate. Apart from the esthetically undesirable shiny and unnatural appearance, a coating will normally make a surface more slippery and prevent water drainage. These properties would be highly undesirable in a surface treatment for asphaltic traffic-bearing areas such as driveways, parking areas, roadways and airport runways for example, and one skilled in the art would avoid such coatings. They would also be ruled out for use on asphalt composition shingles on esthetic grounds.
It was therefore and object of this invention to find a one component surface treatment for asphaltic materials which was free of crosslinking agents and fluorine-free film-forming polymers, which would not impart a shiny and unnatural appearance to treated surfaces, would not impair traction on treated traffic bearing areas and which would extend the useful lifetime of the asphaltic materials by providing protection to asphaltic materials from water, oil and weather damage.
Surprisingly, it has now been found that asphaltic materials, such as traffic bearing areas and roofing materials, can be provided with increased resistance to damage from water, oil and weather, while remaining porous and retaining a natural appearance, by treating them with a composition comprising a dilute aqueous solution or self-dispersed emulsion or dispersion of certain cationic, fluorinated copolymers, optionally in the presence of an effective amount of a penetration assistant.